Gas Powered Subsurface Pump Drive System

ABSTRACT

A gas powered subsurface pump drive system for use in driving a subsurface pump positioned downhole a well and connected to completion tubing includes a pressure connected to the wellhead of the well in fluidic communication with the completion tubing. A pneumatic cylinder is supported above the pressure vessel and has a vertically positioned and reciprocal piston rod extending into the pressure vessel and is connected to an intermediate drive member extends through the production tubing and is connected to a piston rod the subsurface pump for conjoint reciprocation. A pneumatic drive system alternately provides pressurized gas to an instroke port of the pneumatic cylinder and to the pressure vessel to vertically reciprocate the piston rod, the intermediate drive member and the piston rod of the subsurface pump to pump formation fluid upwardly through the tubing.

FIELD OF THE INVENTION

The present invention relates generally to artificial lift systems forlow producing hydrocarbon wells, and more particularly, relating to apneumatic system for driving a lift pump positioned downhole in aproducing gas and/or oil well.

BACKGROUND OF THE INVENTION

When a hydrocarbon well ceases to produce naturally, an artificial liftsystem may be utilized to continue well production. Artificial liftsystems include some sort of mechanical device that is inserted into thewell to lift fluid from the bottom of the well to the surface. Mostcommonly, a subsurface pump is installed in the well at a position thatsubmerges the pump within formation fluid that has accumulated withinthe well casing. The subsurface pump is driven by reciprocating a stringof interconnected sucker rods that are connected to the subsurface pumpand extend the length of the well from the subsurface pump to the groundsurface. Traditionally, a device referred to as a pump jack is installedat the surface that is connected to the string of sucker rods andoperates to reciprocate the string of sucker rods, and thus produceproducts from the well. The pump jack is powered by either an electricmotor or a combustion engine. While pump jacks remain the primary methodfor extracting products from a well, they suffer from many disadvantagesand inefficiencies that include their size and weight, noise pollution,visual pollution, the costs associated with their operation andmaintenance.

To overcome the disadvantages and inefficiencies of pump jacks, varioushydraulic and pneumatic drive mechanisms have been devised to meetvarious needs such as eliminating the need for the pump jack, the use ofsucker rods and reducing operating and maintenance costs. While thesedevices meet their respective objectives and requirements drawbackremain.

Further existing technology requires a source of energy to operate aprime mover to drive the artificial lift system. The prime mover may bean electric motor or combustion engine. Use of an electric motorrequires an electric utility line to be run to the well site or anonsite electrical generator powered by a combustion engine. In mostinstances the costs to run a dedicated electric utility line outweighthe benefit and in some areas it is not possible to run an electricutility. Accordingly, most artificial lift systems whether it is a pumpjack or a hydraulic or pneumatic system utilize a combustion enginerequiring a source of fuel that must be periodically replenished. Gasproduced from the well may be used to fuel the engine but servicing isstill required.

Many wells are located in remote locations that may be inaccessibleduring different times of the year depending on the region in which theis well located which makes operator visits to inspect the well andreplenish fuel difficult, expensive and in some circumstances impossibleduring certain weather seasons.

Accordingly, there is a need for a new artificial lift system thatovercomes the disadvantages as discussed above and inherent in existingtechnology.

SUMMARY OF THE INVENTION

Embodiments of the present invention address this need by providing anartificial lift system which eliminates the use of a pump jack andassociated string of sucker rods.

Embodiments of the present invention also provide an artificial liftsystem which eliminates the requirement of a stuffing box, and thuseliminates the operational and maintenance costs associated therewith.

Embodiments of the present invention further provide an artificial liftsystem including coiled tubing.

Embodiments of the present invention further provide an artificial liftsystem that does not require a combustion engine or an electric utilityline for operation by employing a pneumatically operated pump driverthat that is driven by pressurized gas that can be routed to the wellfrom downstream of the sales gas compressor.

To achieve these and other advantages, in general, in one aspect, a gaspowered subsurface pump drive system for use with a well having awellhead located at the ground surface, a length of completion tubingextending downwardly from the wellhead and a subsurface pump connectedto a lower end of the completion tubing by which formation fluid can bepumped upward through the tubing to the wellhead is provided. The systemincludes a pressure vessel supported above the wellhead and sealingconnected to the wellhead establishing a fluidic connection between theinternal space of the pressure vessel and the completion tubingextending downwardly from the wellhead. A pneumatic cylinder issupported above the pressure vessel and has a vertically positioned andreciprocal piston rod sealing extending into the internal space of thepressure vessel. An intermediate drive member extends through theproduction tubing and couples the piston rod of the pneumatic cylinderand a piston rod of the subsurface pump for conjoint reciprocation. Apneumatic drive system alternately provides pressurized gas to aninstroke port of the pneumatic cylinder and to the pressure vessel tovertically reciprocate the piston rod, the intermediate drive member andthe piston rod of the subsurface pump to pump formation fluid upwardlythrough the tubing.

There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows may be better understood and in order that the presentcontribution to the art may be better appreciated.

Numerous objects, features and advantages of the present invention willbe readily apparent to those of ordinary skill in the art upon a readingof the following detailed description of presently preferred, butnonetheless illustrative, embodiments of the present invention whentaken in conjunction with the accompanying drawings. The invention iscapable of other embodiments and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein are for the purpose of descriptions andshould not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

For a better understanding of the invention, its operating advantagesand the specific objects attained by its uses, reference should be hadto the accompanying drawings and descriptive matter in which there areillustrated embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate by way of example and are included toprovide further understanding of the invention for the purpose ofillustrative discussion of the embodiments of the invention. No attemptis made to show structural details of the embodiments in more detailthan is necessary for a fundamental understanding of the invention, thedescription taken with the drawings making apparent to those skilled inthe art how the several forms of the invention may be embodied inpractice. Identical reference numerals do not necessarily indicate anidentical structure. Rather, the same reference numeral may be used toindicate a similar feature of a feature with similar functionality. Inthe drawings:

FIG. 1 is a diagrammatic illustration of a gas powered subsurface pumpdrive system in accordance with an embodiment of the invention;

FIG. 2 is a diagrammatic illustration of a subsurface pump positioneddownhole a well and connected to a drive member in accordance with anembodiment of the invention;

FIG. 3 is a diagrammatic illustration of a pneumatic cylinder andpressure vessel with the drive member connected to the pneumaticcylinder in accordance with an embodiment of the invention; and

FIG. 4 is ladder diagram of a control circuit of a pneumatic drivesystem of the gas powered subsurface pump drive assembly in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Initially referring to FIG. 1 of the drawings, there is diagrammaticallyillustrated a gas powered subsurface pump drive system 10 according toan embodiment of the invention for pumping formation fluid from a well,such as the representatively illustrated well 12.

Well 12 is a conventional hydrocarbon that produces oil and/or gas andhas the usual borehole, or well-bore 14 having casing 16, formed intothe Earth. The borehole 14 extends from the surface, down through ahydrocarbon producing formation 18 from which fluid flows through casingperforations 20 into the casing annulus 22. While specific discussion ismade herein with respect to an oil and/or gas well, the well could be awater well. Well 12 has a conventional wellhead 24 attached to thesurface end of the well casing 16 and including a blowout preventer(BOP) 26. The wellhead 24 configuration can include different componentssuited for the requirements and/or operation conditions of eachparticular well.

System 10 includes a production tube 28 extending from the wellhead 24down the well casing 16 to a downhole position. The production tube 26may be retained or secured to the wellhead 24 by a conventional tubinghanger (not shown), which is well known in the art. Preferably, theproduction tubing 26 is a length of coiled tubing for specificadvantages over segmented sections of rigid tubing, including beingcapable of being run into the well without killing the well.

A subsurface pump 30 is connected at a bottom 32 of the productiontubing 28. Subsurface pump 30 is a conventional subsurface rod type pump(also may be called a sucker rod pump) that is connectable to theproduction tubing 26 at the surface to be run into the well along withthe production tubing. As best seen in FIG. 2, subsurface pump 30includes an internally disposed piston 34 that is connected to a pistonrod 36 that extends vertically upward from the casing of the pump.Reciprocation of piston rod 36 results in reciprocation of the piston 34and thus pumping of fluid into and out of the pump. The specificconstruction of the subsurface pump 30 forms no part of this inventionand one of ordinary skill in the art will readily recognize numerouspump designs are suitable for use herein. Accordingly, and because suchpumps are well known in the art, a complete technical description of theconstruction of the subsurface pump 30 is not warranted here for theunderstanding and implementation of the embodiments of the invention.

System 10 further includes a pressure vessel 38 having a sealed internalvolume or space 40. The pressure vessel 38 is supported above andsealing connected to the wellhead 24 with the production tubing 28 influidic communication with the internal space 40 of the pressure vessel,as best seen in FIG. 3. Pressure vessel 38 serves to eliminate the useof a stuffing box and several additional purposes that will becomereadily apparent below. The pressure vessel 38 includes a hand port 42that may be unsealed to permit access to the internal space 40.

System 10 further includes a pneumatic cylinder 44. Like conventionalpneumatic cylinders, pneumatic cylinder 44 includes a piston 46 that isinternally disposed for reciprocation therein by gas pressurealternately applied to opposite sides of the piston. A piston rod 48 isconnected to the piston 46, and in turn reciprocates with the piston.The piston rod 48 extends from the housing of the pneumatic cylinderbetween outstroke and instroke positions where the piston rod is fullyextend and fully retracted, respectively. An instroke port 50 isconfigured to receive gas pressure on one side of the piston 46 toretract the piston rod 48. However, in embodiments of the inventionoutstroke port 52 may be utilized to vent gas pressure from thepneumatic cylinder 44.

The pneumatic cylinder 44 is supported vertically above the pressurevessel 38 with the piston rod extending downwardly and into the internalspace 40 of the pressure vessel and in alignment with the productiontubing 28. As illustrated, the lower end 54 is threadably and sealingconnected to a port of the pressure vessel opposite of the wellhead 24.Of course other connections are possible that provide a sealingconnection between at least the piston rod 48 of the pneumatic cylinder44 and the pressure vessel 38, and which may also support the pneumaticcylinder.

An intermediate drive member 56 extends the length of the productiontubing 28 and internally therewithin. The intermediate drive member 56is connected at a top end to piston rod 48 within the pressure vessel 38and is connected at a bottom end to the piston rod 36 of the subsurfacepump 30. While it is possible for the intermediate drive member 56 tocomprise a string of sucker rods, it is preferred that the intermediatedrive member is a flexible cable. The flexible cable is preferredbecause an assembly comprising the coiled production tubing 28, thesubsurface pump 30 and the intermediate drive member 56 may beconstructed at the surface and then run into the well without killingthe well.

System 10 further includes a pneumatic drive system 58, as best seen inFIG. 1. The pneumatic drive system 58 utilizes the existing crudeformation fluid pipeline 60 installed at the wellsite for receiving andtransporting formation fluid produced by the well to a location remotefrom the wellsite. The pneumatic drive system 58 also utilizes a salesgas pipeline 62 installed at the wellsite for transporting compressednatural gas to the wellsite from a location remote of the wellsite. Thepneumatic drive system 58 utilizes the relatively higher pressure gas inpipeline 62 (for example 200 PSI) and relatively lower pressure inpipeline 60 (for example, less than 50 PSI) in driving the pneumaticcylinder 44, and thus, the subsurface pump 30 to pump formation fluidfrom the well. To this end, the pneumatic drive system 58 is configuredto alternately providing pressurized gas to the instroke port 50 of thepneumatic cylinder 44 and to the pressure vessel 38 and to alternatelyvent the pressurized gas from the pneumatic cylinder 44 and the pressurevessel 38 to vertically reciprocate the piston rod 48, the intermediatedrive member 56 and the piston rod 36 of the subsurface pump 30 to pumpformation fluid upwardly through the tubing.

More specifically, an in an embodiment, the pneumatic drive system 58operates to provide relatively high gas pressure at the instroke port 50of the pneumatic cylinder 44 from pipeline 62 and to simultaneouslyconnect the internal space 40 of the pressure vessel 38 to therelatively low pressure of pipeline 60 to cause an instroke action onthe piston rod 48 of the pneumatic cylinder, and thus, also stroke theintermediate drive member 56 and the piston rod 36 of the subsurfacepump. Once the instroke action is completed, the pneumatic drive system58 then operates to provide relatively high gas pressure to the internalspace 40 of the pressure vessel 38 to pressurize the column of formationfluid (which is relatively incompressible fluid) in the productiontubing 28 and to simultaneously connect the instroke port 50 of thepneumatic cylinder 44 to the relatively low pressure of pipeline 60 tovent the gas pressure therefrom to cause reset or an outstroke action onthe piston rod 48 of the pneumatic cylinder by downwardly stroking thepiston rod 36 of the subsurface pump 30 as a result of the head pressureon the column of formation fluid acting on the subsurface pump. Thisprocess is repeated until a desired amount of formation fluid is pumpedfrom the well 12.

In an embodiment of the pneumatic drive system 58, fluid line 64conventionally connects the wellhead 24 to the pipeline 60 to receiveproduced (pumped) formation fluid from the production tubing 28. Fluidline 64 is illustrated diagrammatically and in a simplified form and maycontain many different systems installed along fluid line from thewellhead to the pipeline 60. The instroke port 50 of the pneumaticcylinder 44 is alternately connected to pipeline 62 receive gas pressuretherefrom and to pipeline 60 to vent gas pressure from the instroke portside of the pneumatic cylinder to the lower pressure pipeline 60 torecover the natural gas. An instroke port valve 66 is fluidicallyconnected by line 68 to the instroke port 50, is fluidically connectedto pipeline 60 by line 70 and is fluidically connected to pipe line 62by line 72. Instroke port valve 66 is configured and operated toselectively establish a fluid flow between lines 68 and 72 to connectthe instroke port 50 to pipeline 62 to receive gas pressure therefrom,and to establish a fluid flow between lines 68 and 70 to connect theinstroke port 50 to pipeline 60 to vent gas pressure from instroke portto pipeline 60. The pressure vessel 38 is likewise alternately connectedto pipeline 62 receive gas pressure therefrom and to pipeline 60 to ventgas pressure from the pressure vessel to the lower pressure pipeline 60to recover the natural gas. A pressure vessel valve 74 is fluidicallyconnected by line 76 to the internal space 40 of the pressure vessel 38,is fluidically connected to pipeline 60 by line 78 and is fluidicallyconnected to pipe line 62 by line 80. Pressure vessel valve 74 isconfigured and operated to selectively establish a fluid flow betweenlines 76 and 80 to connect the internal space 40 of the pressure vessel38 to pipeline 62 to receive gas pressure therefrom, and to establish afluid flow between lines 76 and 78 to connect the internal space of thepressure vessel to the lower pressure pipeline 60 to vent gas pressuretherefrom.

In the same embodiment, the pneumatic drive system further includes afirst pressure switch or sensor 82 that is connected to the pressurevessel 38 via line 76 to measure the gas pressure in the internal space40. A second pressure switch or sensor 84 is connected to the instrokeport 50 via line 68 to measure the gas pressure of the pneumaticcylinder 44 at the instroke port thereof. Pressure switch 82, pressureswitch 84, valve 66 and valve 74 are connected to a control circuit 86which operates to control valves 66 and 74 based upon pressure atpressure switches 82 and 84 to alternately provide pressurized gas frompipeline 62 to the instroke port 50 of the pneumatic cylinder 44 and tothe pressure vessel 38 to vertically reciprocate the piston rod 48, theintermediate drive member 56 and the piston rod 36 of the subsurfacepump 30 to pump formation fluid upwardly through the tubing.

With reference to FIG. 4, there is illustrated a ladder diagramaccording to an embodiment of the control circuit 86. In thisembodiment, the control circuit includes a 12V power source 88 (such asa small battery that may be recharged by solar energy), a main powerswitch 90, a timer 92, a first control relay 94, a second control relay96, a solenoid operator 98 of valve 66, a solenoid operator 100 of valve74, the first pressure switch 76 and the second pressure switch 84.

With continued reference to FIG. 4, in an embodiment, the timer 92 isprogrammed to operate the control circuit 86 at desired times and daysdepending upon the requirements of the well. The timer may be modifiedas well requirements change. Initially, the following control sequencystarts from the piston rod 48 of the pneumatic cylinder 44 in theextended or outstroked position. Upon wakeup of the timer 92, controlrelay 96 operates to energize solenoid operator 100 of valve 66 toestablish a fluid connection between lines 68 and 72, and therebyprovide gas pressure at instroke port 50 of the pneumatic cylinder 44.Valve 74 is normally set to establish a fluid connection between lines76 and 78, and thus is at low pressure relative to the gas pressure ofpipeline 62. Gas pressure at instroke port 50 causes the piston rod 48of the pneumatic cylinder 44 to instroke which results in stroking ofthe intermediate drive member 56 and the piston rod 36 of the subsurfacepump 30. A completed instroke of piston rod 48 is determined by apressure rise at instroke port 50 which is measured by pressure switch84. Once the pressure at instroke port 50 reaches a predeterminedpressure, pressure switch 84 is activated which results in control relay94 operating to de-energize solenoid operator 100 of valve 66, therebyconnecting lines 68 and 70 to permit venting of gas pressure from thepneumatic cylinder 44 through instroke port 50 and into pipeline 60.Activation of pressure switch 84 also results in control relay 96energizing the solenoid operator 98 of valve 74 to establish a fluidconnection between lines 76 and 80, and thus pressurize the internalspace 40 of the pressure vessel 38 by pressurized gas from pipeline 62.Pressurization of internal space 40 increases the head pressure of thecolumn of formation fluid in the production tubing 28 causing a reset oran outstroke action on the piston rod 48 of the pneumatic cylinder bydownwardly stroking the piston rod 36 of the subsurface pump 30 as aresult of the head pressure on the column of formation fluid acting onthe subsurface pump. A completed reset or outstroke of piston rod 48 isdetermined by a pressure rise in the internal space 40 which is measuredby pressure switch 82. Once the pressure of the internal space 40reaches a predetermined pressure, pressure switch 82 is activated whichresults in control relay 96 operating to de-energize solenoid operator98 and control relay 92 once again operating solenoid operator 100 tostart the process over again. This process continues until timer 92enters a sleep mode.

In embodiments, port 52 of the pneumatic cylinder 44 may be connected topipeline 60 by connection to vent any well gas that may have migratedacross the piston 46 of the pneumatic cylinder to the pipeline toprevent air pollution from a sour well. In other embodiments, port 52 isvented to atmosphere.

A number of embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. A gas powered subsurface pump drive system for use with a well havinga wellhead located at the ground surface, a length of completion tubingextending downwardly from the wellhead and a subsurface pump connectedto a lower end of the completion tubing by which formation fluid can bepumped upward through the tubing to the wellhead, the system comprising:a pressure vessel supported above the wellhead and sealing connected tosaid wellhead establishing a fluidic connection between the internalspace of said pressure vessel and the completion tubing extendingdownwardly from the wellhead; a pneumatic cylinder supported above saidpressure vessel, said pneumatic cylinder having a vertically positionedand reciprocal piston rod sealing extending into said internal space ofsaid pressure vessel; an intermediate drive member extending through theproduction tubing and coupling said piston rod of said pneumaticcylinder and a piston rod of the subsurface pump for conjointreciprocation; and a pneumatic drive system alternately providingpressurized gas to an instroke port of said pneumatic cylinder and tosaid pressure vessel to vertically reciprocate said piston rod, saidintermediate drive member and the piston rod of the subsurface pump topump formation fluid upwardly through the tubing.
 2. The system of claim1, wherein said pressurized gas is gas from a sales gas pipeline from aproduction plant located remotely from the well.
 3. The system of claim2, wherein said pneumatic system further alternately discharges saidpressurized gas from said instroke port of said pneumatic cylinder andsaid pressurized vessel into a crude formation fluid pipeline to saidproduction plant.
 4. The system of claim 3, wherein an outstroke port ofsaid pneumatic cylinder is vented to atmosphere.
 5. The system of claim3, wherein an outstroke port of said pneumatic cylinder is connected tosaid crude formation fluid pipeline.
 6. The system of claim 1, whereinthe production tubing is coiled tubing.
 7. The system of claim 1,wherein said intermediate drive member is a flexible cable.
 8. Thesystem of claim 1, wherein the wellhead is connected to a crudeformation fluid pipeline to receive pumped formation fluid at a positionvertically lower elevation than connection between said pressure vesseland said wellhead.
 9. The system of claim 1, wherein said pneumaticdrive system operates to measure gas pressure at said instroke port andto measure gas pressure at said pressure vessel, and as a function ofsaid measured gas pressures alternately provides said pressurized gas tosaid instroke port and to said pressure vessel.